Added structlog support (#109)

- Adds `StructlogCapturer` and related docs. Follows `loguru` extension structure, borrowing inspiration from the structlog testing tools. I've matched the suggested version range in hynek/structlog#596. Closes #108
etianen · Feb 17, 2024 · e7349c6 · e7349c6
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diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
@@ -19,6 +19,8 @@ jobs:
           - python-version: "3.10"
           - python-version: "3.11"
           - python-version: "3.12"
+          - lib-versions: "structlog~=23.3.0"
+          - lib-versions: "structlog~=24.1.0"
           - lib-versions: "loguru~=0.6.0"
           - lib-versions: "loguru~=0.7.0"
           - lib-versions: "pytest~=7.0"

diff --git a/README.md b/README.md
@@ -9,32 +9,28 @@
 
 `logot` makes it easy to test whether your code is logging correctly:
 
-``` python
+```python
 from logot import Logot, logged
 
 def test_something(logot: Logot) -> None:
     do_something()
     logot.assert_logged(logged.info("Something was done"))
 ```
 
-`logot` integrates with popular testing (e.g. [`pytest`](https://logot.readthedocs.io/latest/using-pytest.html), [`unittest`](https://logot.readthedocs.io/latest/using-unittest.html)), asynchronous (e.g. [`asyncio`](https://logot.readthedocs.io/latest/index.html#index-testing-threaded), [`trio`](https://logot.readthedocs.io/latest/integrations/trio.html)) and logging frameworks (e.g. [`logging`](https://logot.readthedocs.io/latest/log-capturing.html), [`loguru`](https://logot.readthedocs.io/latest/integrations/loguru.html)). It can be extended to support many others. 💪
-
+`logot` integrates with popular testing (e.g. [`pytest`](https://logot.readthedocs.io/latest/using-pytest.html), [`unittest`](https://logot.readthedocs.io/latest/using-unittest.html)), asynchronous (e.g. [`asyncio`](https://logot.readthedocs.io/latest/index.html#index-testing-threaded), [`trio`](https://logot.readthedocs.io/latest/integrations/trio.html)) and logging frameworks (e.g. [`logging`](https://logot.readthedocs.io/latest/log-capturing.html), [`loguru`](https://logot.readthedocs.io/latest/integrations/loguru.html), [`structlog`](https://logot.readthedocs.io/latest/integrations/structlog.html)). It can be extended to support many others. 💪
 
 ## Documentation 📖
 
 Full documentation is published on [Read the Docs](https://logot.readthedocs.io).
 
-
 ## Bugs / feedback 🐛
 
 Issue tracking is hosted on [GitHub](https://github.com/etianen/logot/issues).
 
-
 ## Changelog 🏗️
 
 Release notes are published on [GitHub](https://github.com/etianen/logot/releases).
 
-
 ## License ⚖️
 
 `logot` is published as open-source software under the [MIT license](https://github.com/etianen/logot/blob/main/LICENSE).
diff --git a/docs/api/logot.structlog.rst b/docs/api/logot.structlog.rst
@@ -0,0 +1,10 @@
+:mod:`logot.structlog`
+=======================
+
+.. automodule:: logot.structlog
+
+
+API reference
+-------------
+
+.. autoclass:: StructlogCapturer
diff --git a/docs/conf.py b/docs/conf.py
@@ -27,6 +27,7 @@
 intersphinx_mapping = {
     "python": ("https://docs.python.org/3/", None),
     "loguru": ("https://loguru.readthedocs.io/en/latest/", None),
+    "structlog": ("https://www.structlog.org/en/stable/", None),
     "pytest": ("https://docs.pytest.org/en/latest/", None),
     "trio": ("https://trio.readthedocs.io/en/latest/", None),
 }

diff --git a/docs/index.rst b/docs/index.rst
@@ -18,7 +18,8 @@ Log-based testing 🪵
    :mod:`logot` integrates with popular testing (e.g. :doc:`pytest </using-pytest>`,
    :doc:`unittest </using-unittest>`), asynchronous (e.g. :ref:`asyncio <index-testing-threaded>`,
    :doc:`trio </integrations/trio>`) and logging frameworks (e.g. :doc:`logging </log-capturing>`,
-   :doc:`loguru </integrations/loguru>`). It can be extended to support many others. 💪
+   :doc:`loguru </integrations/loguru>`, :doc:`structlog </integrations/structlog>`). It can be extended
+   to support many others. 💪
 
 
 Why test logging? 🤔

diff --git a/docs/integrations/index.rst b/docs/integrations/index.rst
@@ -47,6 +47,7 @@ Supported frameworks:
    :maxdepth: 1
 
    loguru
+   structlog
 
 .. seealso::
 

diff --git a/docs/integrations/structlog.rst b/docs/integrations/structlog.rst
@@ -0,0 +1,95 @@
+Using with :mod:`structlog`
+============================
+
+.. currentmodule:: logot
+
+:mod:`logot` makes it easy to capture logs from :mod:`structlog`:
+
+.. code:: python
+
+   from logot.structlog import StructlogCapturer
+
+   with Logot(capturer=StructlogCapturer).capturing() as logot:
+      do_something()
+      logot.assert_logged(logged.info("App started"))
+
+:mod:`logot` preserves the preconfigured :mod:`structlog` processor chain. Events are captured at the end of the chain,
+but before the final processor, as it is responsible for emitting the log event to the underlying logging system. For
+more information, see the
+`structlog documentation <https://www.structlog.org/en/stable/processors.html#adapting-and-rendering>`_.
+
+
+Installing
+----------
+
+Ensure :mod:`logot` is installed alongside a compatible :mod:`structlog` version by adding the ``structlog`` extra:
+
+.. code:: bash
+
+   pip install 'logot[structlog]'
+
+.. seealso::
+
+   See :ref:`installing-extras` usage guide.
+
+
+Enabling for :mod:`pytest`
+--------------------------
+
+Enable :mod:`structlog` support in your :external+pytest:doc:`pytest configuration <reference/customize>`:
+
+.. code:: ini
+
+   # pytest.ini or .pytest.ini
+   [pytest]
+   logot_capturer = logot.structlog.StructlogCapturer
+
+.. code:: toml
+
+   # pyproject.toml
+   [tool.pytest.ini_options]
+   logot_capturer = "logot.structlog.StructlogCapturer"
+
+.. seealso::
+
+   See :doc:`/using-pytest` usage guide.
+
+
+Enabling for :mod:`unittest`
+----------------------------
+
+Enable :mod:`structlog` support in your :class:`logot.unittest.LogotTestCase`:
+
+.. code:: python
+
+   from logot.structlog import StructlogCapturer
+
+   class MyAppTest(LogotTestCase):
+      logot_capturer = StructlogCapturer
+
+.. seealso::
+
+   See :doc:`/using-unittest` usage guide.
+
+
+Enabling manually
+-----------------
+
+Enable :mod:`structlog` support for your :class:`Logot` instance:
+
+.. code:: python
+
+   from logot.structlog import StructlogCapturer
+
+   logot = Logot(capturer=StructlogCapturer)
+
+Enable :mod:`structlog` support for a single :meth:`Logot.capturing` call:
+
+.. code:: python
+
+   with Logot().capturing(capturer=StructlogCapturer) as logot:
+      do_something()
+
+.. seealso::
+
+   See :class:`Logot` and :meth:`Logot.capturing` API reference.
diff --git a/docs/log-capturing.rst b/docs/log-capturing.rst
@@ -13,7 +13,7 @@ Log capturing
 
 .. seealso::
 
-   See :ref:`integrations-logging` for other supported logging frameworks (e.g. :doc:`loguru </integrations/loguru>`).
+   See :ref:`integrations-logging` for other supported logging frameworks (e.g. :doc:`loguru </integrations/loguru>`, :doc:`structlog </integrations/structlog>`).
 
 
 Test framework integrations

diff --git a/docs/using-pytest.rst b/docs/using-pytest.rst
@@ -37,7 +37,8 @@ using |caplog|_ as:
 - Support for :doc:`log message matching </log-message-matching>` using ``%``-style placeholders.
 - Support for :doc:`log pattern matching </log-pattern-matching>` using *log pattern operators*.
 - Support for testing :ref:`threaded <index-testing-threaded>` and :ref:`async <index-testing-async>` code.
-- Support for :ref:`3rd-party logging frameworks <integrations-logging>` (e.g. :doc:`loguru </integrations/loguru>`).
+- Support for :ref:`3rd-party logging frameworks <integrations-logging>` (e.g. :doc:`loguru </integrations/loguru>`,
+  :doc:`structlog </integrations/structlog>`).
 - A cleaner, clearer syntax.
 
 

diff --git a/docs/using-unittest.rst b/docs/using-unittest.rst
@@ -43,7 +43,8 @@ testing. The above example can be rewritten using :meth:`assertLogs() <unittest.
 - Support for :doc:`log message matching </log-message-matching>` using ``%``-style placeholders.
 - Support for :doc:`log pattern matching </log-pattern-matching>` using *log pattern operators*.
 - Support for testing :ref:`threaded <index-testing-threaded>` and :ref:`async <index-testing-async>` code.
-- Support for :ref:`3rd-party logging frameworks <integrations-logging>` (e.g. :doc:`loguru </integrations/loguru>`).
+- Support for :ref:`3rd-party logging frameworks <integrations-logging>` (e.g. :doc:`loguru </integrations/loguru>`,
+  :doc:`structlog </integrations/structlog>`).
 - A cleaner, clearer syntax.
 
 

diff --git a/logot/_structlog.py b/logot/_structlog.py
@@ -0,0 +1,53 @@
+from __future__ import annotations
+
+from functools import partial
+
+import structlog
+from structlog.processors import NAME_TO_LEVEL
+from structlog.types import EventDict, WrappedLogger
+
+from logot._capture import Captured
+from logot._logot import Capturer, Logot
+from logot._typing import Level, Name
+
+
+class StructlogCapturer(Capturer):
+    """
+    A :class:`logot.Capturer` implementation for :mod:`structlog`.
+    """
+
+    __slots__ = ("_old_processors",)
+
+    def start_capturing(self, logot: Logot, /, *, level: Level, name: Name) -> None:
+        config = structlog.get_config()
+        processors = config["processors"]
+        self._old_processors = processors
+
+        if isinstance(level, str):
+            levelno = NAME_TO_LEVEL[level.lower()]
+        else:
+            levelno = level
+
+        # We need to insert our processor before the last processor, as this is the processor that transforms the
+        # `event_dict` into the final log message. As this depends on the wrapped logger's formatting requirements,
+        # it can interfere with our capturing.
+        # See https://www.structlog.org/en/stable/processors.html#adapting-and-rendering
+        structlog.configure(
+            processors=[*processors[:-1], partial(_processor, logot=logot, name=name, levelno=levelno), processors[-1]]
+        )
+
+    def stop_capturing(self) -> None:
+        structlog.configure(processors=self._old_processors)
+
+
+def _processor(
+    logger: WrappedLogger, method_name: str, event_dict: EventDict, *, logot: Logot, name: Name, levelno: int
+) -> EventDict:
+    msg = event_dict["event"]
+    level = method_name.upper()
+    event_levelno = NAME_TO_LEVEL[method_name]
+
+    if getattr(logger, "name", None) == name and event_levelno >= levelno:
+        logot.capture(Captured(level, msg, levelno=event_levelno))
+
+    return event_dict
diff --git a/logot/structlog.py b/logot/structlog.py
@@ -0,0 +1,10 @@
+"""
+Integration API for :mod:`structlog`.
+
+.. seealso::
+
+    See :doc:`/integrations/structlog` usage guide.
+"""
+from __future__ import annotations
+
+from logot._structlog import StructlogCapturer as StructlogCapturer
diff --git a/poetry.lock b/poetry.lock
diff --git a/pyproject.toml b/pyproject.toml
@@ -25,12 +25,14 @@ packages = [{ include = "logot" }]
 [tool.poetry.dependencies]
 python = "^3.8"
 loguru = { version = ">=0.6,<0.8", optional = true }
+structlog = { version = ">=23.3,<25", optional = true }
 pytest = { version = ">=7,<9", optional = true }
 trio = { version = ">=0.22,<0.25", optional = true }
 typing-extensions = { version = ">=4.9", python = "<3.10" }
 
 [tool.poetry.extras]
 loguru = ["loguru"]
+structlog = ["structlog"]
 pytest = ["pytest"]
 trio = ["trio"]
 
@@ -75,6 +77,8 @@ addopts = "--tb=native --import-mode=importlib"
 [tool.ruff]
 include = ["docs/**/*.py", "logot/**/*.py", "tests/**/*.py"]
 line-length = 120
+
+[tool.ruff.lint]
 select = ["E", "F", "W", "I", "UP"]
 
 [build-system]